1. Field of the Invention
The present invention relates to a wheel bearing device of a vehicle such as an automobile.
2. Description of the Related Art
Wheel bearing devices are generally classified into those for drive-wheel applications and for driven-wheel applications. A drive wheel bearing device is commonly composed of a wheel hub and a double-row bearing, or a unit of a wheel hub, a bearing, and a constant velocity joint.
One of the drive wheel bearing device designs has a construction in which one of the double-row inner races of the bearing is formed on the outer periphery of the wheel hub, while the other is formed on the outer periphery of an outer joint member of the constant velocity joint. In this type of bearing device, the wheel hub and the constant velocity joint need to be joined together to achieve relative positioning of the double-row inner races and to maintain certain preload applied to the inside of the bearing. There has been a new method of joining them by swaging as shown, e.g., in Japanese Patent Laid-Open Publication No. 2001-18605, for better use of axial space of the bearing and for the enhancement of the joint rigidity of a plastically deformed portion. With this method, a stem part of the outer joint member is expanded radially outward by plastic deformation so that it firmly engages with irregularities formed on the inner periphery of the wheel hub.
Generally, the wheel bearing device in a vehicle takes a large bending moment when the vehicle turns. Various constituent elements of the bearing device thus suffer from large, local bending stress because of this bending moment. The swaged type bearing device mentioned above does not give sufficient consideration to this point, and therefore it may have lower durability or shorter life than desired.